The present invention relates generally to core-type aerators, and more particularly to a driven tine wheel core-type aerator having novel tine geometry.
It is common practice in the treating of turf, such as on golf courses and similar groomed lawn areas, to aerate the turf by forming a pattern of generally cylindrical shaped holes in the turf which enable moisture and fertilizers and the like to more readily reach and stimulate root growth, thus leading to a heartier turf. The aeration holes are conventionally formed by apparatus, termed aerators, which include a plurality of coring tines operative to penetrate the soil in a manner to remove generally cylindrical cores or plugs of turf. In one type of aerator for effecting core aerification, the tines are mounted in generally radial relation about a tine wheel which is adapted to rotate about an axis transverse to the direction of movement of the aerator. The tines are conventionally mounted in circumferentially spaced rows such that the tines sequentially penetrate the soil on rotation of the tine wheel to create a pattern of aeration holes.
Aerators of the rotary tine wheel type are generally further classified as being either towed type aerators wherein the tine wheels are supported for substantially free rotation about their longitudinal axes and are caused to rotate in response to towing of the aerator by a tractor or the like through a drawbar or three-point hitch arrangement, or driven tine wheel type aerators wherein the tine wheel has positive driven relation with motor means or the like carried by the aerator and operative when energized to cause the tine wheel to rotate so as to propel the aerator while simultaneously effecting tine penetration to aerate the underlying turf. Significant differences exist between these two types of aerators which influence the specific tine geometry best suited for each type aerator.
For example, the forces delivered to the soil through the tines, termed the tine penetration forces, are different for towed and driven tine wheel aerators. This difference dictates the need for different tine angles between towed and driven tine wheels. By tine angle is meant the angular relation between the longitudinal axis of the turf penetrating end of the tine and a radius extending from the rotational axis of the tine wheel and generally intersecting the point at which the tine extends from the tine wheel periphery. This relation may also be termed the tine orientation geometry. For a towed type tine wheel, two forces must be supported by the soil; a component of the drawbar pulling force, and the weight of the machine. A driven type tine wheel also has two forces that must be supported by the soil; the weight of the machine and the resultant force of the driving torque acting on the tine wheel. This resultant driving torque force is generally larger than the drawbar component force of a towed type tine wheel so that the weight required to effect the same aerating core depth is generally less for a driven tine wheel type aerator. The differences in tine penetration forces between towed and driven tine wheel type aerators also change the instant center of rotation, or true rolling radius, of the tine wheel; specifically, the instant center of the driven tine wheel tends to be deeper in the soil than for a towed type tine wheel. This difference necessitates different tine angles or tine orientation geometry for the driven type tine wheels to provide optimum aerating performance.
A desirable objective of rotary tine wheel type aerators, and particularly aerators employed to aerate golf course greens or other areas where relatively even surfaces are critical, is to form the aerification holes with minimum disturbance or lifting of the turf peripherally about the hole openings.
An example of a towed type rotary tine wheel aerator is disclosed in U.S. Pat. No. 2,580,236 to Mascaro. The Mascaro patent recognizes the problem often encountered in aerating turf having a relatively shallow grass root structure; that is, the tendency of the aerating tines to tear loose and raise the surface layer of turf adjacent the formed aerating holes. Mascaro attempts to overcome this problem by utilizing coring tines or spoons which after initial entry into the turf at generally right angles to the turf surface move progressively rearwardly to undercut the subsoil in an arcuate sweeping action about a center located substantially at the entrance of the tine into the turf. This action is believed to create an uplifting force on the turf overlying the arcuate sweep of the tine, thus creating, rather than solving, the very problem recognized by Mascaro. Mascaro suggests overcoming the problem of uplifting of the turf surface by providing bearing elements or strips which engage the upper surface of the turf between the coring tines or spoons.